The uncle in charge of an 8-year-old boy who took a toddler onto a Brooklyn roof where he plunged to his death was let off the hook yesterday.

Cops arrested Kareem Strickland for child endangerment, but then dropped the charges after the Brooklyn District Attorney’s Office ruled he could not have anticipated the tragedy.

Strickland, 26, was supposed to be watching his nephew, but was inside his apartment when the boy led his little pal to the roof of the Crown Heights building where he fell Tuesday night, cops said.

Zaire Gonzalez, 4, was accidentally knocked off a ledge by the boy and tumbled four stories into a courtyard below, cops said.

Strickland was arrested shortly afterward and released yesterday.

“We don’t believe he could have foreseen this,” said Brooklyn DA spokesman Jerry Schmetterer. “This was a tragedy, but we do not see any criminality involved.” The deadly mishap unfolded after the boys began playing outside the building at 1451 Prospect Place, where the 8-year-old lived with his uncle and mother, neighbors said. The uncle stayed home, leaving the boys unsupervised, cops said.

Zaire’s mom, Joy Gonzalez, meanwhile, had left him in the care of his 13-year-old sister, who relatives said picked him up from a nearby day-care center shortly before the tragedy.

The 13-year-old then left him briefly with a group of children while going back to pick up another child, sources said.

Shortly after 7 p.m., Zaire and the 8-year-old broke away from their pals and headed to the roof of 1451 Prospect Place.

The boy told cops it was the first time they had ventured up there.

“One of the kids he was playing with lured him,” said Zaire’s devastated grandmother, Joyce Gonzalez. She said her daughter was too upset to speak about the loss of her son.

“It’s very hard for them, she’s broke apart,” said a family friend. A neighbor, whose 10-year-old son played with the boys, said all the kids in the building regularly played outside – but were banned from going to the roof.

“I always tell the kids not to play in the hallway or on the street or on the rooftop,” said Yvette Wells, 41.

Yesterday neighbors set up two memorials for the tot, placing photos and candles outside the building the tragedy happened and his home next door.